The present invention relates to novel sensitizers of diazo fluorinated esters containing the hexafluoroisopropylidene group. The diazo photosensitizers of the invention are extremely compatible with fluorinated hydroxy polyamides, are soluble in commonly used solvents and, in combination with fluorinated hydroxy polyamides, and other hydroxy resins such as, hydroxy styrenes or Novolaks, provide photosensitive compositions which, when coated on a suitable substrate, provide a uniform coating and develop well in light/dark regions.
Applications Ser. No. 915,342 and Ser. No. 124,634, the disclosures of which are incorporated herein by reference thereto, relate to fluorinated hydroxy polyamide polymers having hexafluoroisopropylidene linking groups and their use in making base developable positive acting high speed photoresists. The present invention relates to esters which are produced from hexafluoro-bis-phenols and bis-hexafluoroethers which can be used to produce the aminophenols and aminoethers useful in the production of the fluorinated hydroxy polyamide resins disclosed in said applications and to photosensitive compositions which comprise the sensitizers of the present invention in combination the fluorinated hydroxy polyamide resins disclosed in said applications.
Generally, polyamide photosensitive compositions are available as high temperature-resistant resinous compositions which are soluble in conventional alkaline solvents and developers. This solubility is preserved in the positive photoresist process in which the exposed, uncoupled areas of the photoresist coating retain their original solubility while the unexposed masked areas are coupled with an azo photosensitzer to a condition in which they are rendered insoluble in alkaline developers. Reference is made to U.S. Pat. Nos. 4,093,461; 4,339,521 and 4,395,482 which disclose such positive-acting photoresist compositions.
In the industrial application of positive photoresists, the polymeric component and the radiation sensitizer are dissolved in an organic solvent or mixture of solvents and applied as a thin film or coating to a substrate suitable for the desired application.
The polymeric component of these photoresist formulations is desirably soluble in aqueous alkaline solutions, but the sensitizer acts as a dissolution rate inhibitor with respect to the polymer. Upon exposure of selected areas of the coated substrate to actinic radiation, the sensitizer undergoes a radiation induced structural transformation and the exposed areas of the coating are rendered more soluble than the unexposed areas. This difference in solubility rates normally causes the exposed areas of the photoresist coating to be dissolved when the substrate is immersed in alkaline developing solution leaving the unexposed areas substantially intact, thus producing a positive relief pattern on the substrate.
In most applications, the exposed and developed substrate will be subjected to treatment by a substrate-etchant solution. The resist coating protects the coated areas of the substrate from the etchant and thus the etchant is only able to etch the uncoated areas of the substrate, which in the case of a positive photoresist, corresponds to the areas that were exposed to actinic radiation. Thus, an etched pattern can be created on the substrate which is a positive of the pattern of the mask, stencil, template, etc., that was used to create selective exposure patterns on the coated substrate prior to development.
The relief pattern of photoresist on the substrate produced by the methods described above is useful for various applications including, for example, as an exposure mask or a pattern such as is employed in the manufacture of miniaturized integrated electronic components or the manufacture of a printing plate.
The properties of a photoresist composition which are important in commercial practice include the solubility of the photoresist in the application solvent, the photospeed of the photoresist, development contrast, environmentally acceptable developer solubility, photoresist resolution and adhesion, dimensional stability at elevated temperature and abrasion resistance.
Photospeed is important for a photoresist, particularly in applications where a number of exposures are needed, for example, in generating multiple patterns by a repeated process, or where light of reduced intensity is employed, such as in projection exposure techniques where the light is passed through a series of lenses and mono-chromatic filters. Thus, high, controlled photospeed is particularly important for a photoresist composition employed in processes where a number of multiple exposures must be made to produce a mask or series of circuit patterns on a substrate. Control of the photospeed is extremely important in order to produce high resolution relief patterns in microcircuitry; e.g., a photospeed too high can result in narrowing the processing conditions.
Photoresist resolution refers to the capability of a photoresist system to reproduce the smallest equally spaced line pairs and intervening spaces of a mask which is utilized during exposure with a high degree of image edge acuity in the developed exposed spaces. In many industrial applications, particularly in the manufacture of miniaturized electronic components, a photoresist is required to provide a high degree of resolution for very small line and space widths (on the order of about a micron).
The ability of a photoresist to reproduce very small dimensions, on the order of about a micron, is extremely important in the production of large scale integrated circuits on silicon chips and similar components. Circuit density on such a chip can be increased, assuming photolithography techniques are utilized, by increasing the resolution capabilities of the resist.
Various attempts have been made in the prior art to produce high temperature positive photoresists possessing the above desired properties. For example, co-pending application Ser. No. 363,245, filed Jun. 8, 1989, relates to hydroxylated polyamide and polyimide polymers, wherein a predetermined percentage of the hydroxy groups are reacted with an azo quinone sulfonyl chloride photosensitizer to form unitary self-sensitive polymers useful for photoresist compositions. However, the self-photosensitized polymers of this application have predetermined solubility properties which develop predetermined degrees of alkali-solubility upon exposure to actinic radiation. Thus, once the basic polymer is produced, the predetermined solubility properties cannot be changed. This means that large inventories must be retained of polymers having varying solubility properties and the producer must accurately predict the solubility characteristics of photoresists to be ordered in the future.
U.S. Pat. No. 4,093,461 discloses a heat resistant, positive photoresist composition comprising a quinone or naphthoquinone diazide and the polycondensation product of an aromatic dianhydride (pryomellitic anhydride) and an aromatic diamine (4,4'-diaminodiphenylether). The properties of the positive photoresist of the patent are discussed in U.S. Pat. No. 4,395,482 (column 1, lines 46-64). There it is pointed out that the positive photoresist composition of U.S. Pat. No. 4,093,461 has limited storage life, insufficient stability to alkaline etching solutions and relatively small differences in solubility between the exposed and unexposed portions of the photoresist.
The exceptional dielectric and high temperature resistance properties of polyamides make them particularly useful in the semiconductor industry. They can be used, for example, as dielectric layers, alpha particle barriers in memory devices, ion implantation masks and passivation layers. The goal of numerous development programs has been the development of a simple, reliable and cost effective radiation sensitive polyamide system that could be used with common photolithographic equipment and processes.
The present invention uses the fluorinated hydroxy polyamides of application Ser. No. 915,342 or Ser. No. 124,634 as a binder material to provide positive photosensitive compositions; e.g., an alkali soluble fluorinated hydroxy polyamide in combination with the novel diazo fluorinated sensitizer of the present invention to provide novel high temperature-resistant photosensitive compositions having easily adjustable base solubilities, good shelf life, rapid development and cure properties and high dimensional stability, for producing uniform patterns with excellent resolution and adhesion properties.
The fluorinated diazo sensitizers of the present invention are also applicable for making photorisist invention are also compositions using Novolaks, Hydroxy styrene type resin and hydroxy polyimide type resins disclosed in U.S. Pat. No. 4,927,736.